There has been demand in a wide variety of fields for an aromatic iodine compound in which an iodine atom is bound to a nucleus of an aromatic compound, as an intermediate used for various organic synthesis. In order to produce such an aromatic iodine compound, a method of using an iodine cation has been known. In the method, the iodine cation generated by electrolysis is used as an iodizing agent (see Patent Literature 1 and Non Patent Literatures 1 through 3). The iodine cation is a significantly-effective iodizing agent having high reactivity. For example, Non Patent Literatures 1 and 2 disclose a method of producing an iodine cation by electrolyzing iodine molecules by using metal salt as a supporting electrolyte in an organic solvent (acetonitrile). Further, Non Patent Literatures 1 and 2 disclose that the iodine cation thus obtained was caused to react with various aromatic compounds. Furthermore, Non Patent Literature 3 discloses a method of producing an iodine cation by using quaternary ammonium salt as a supporting electrolyte.
Meanwhile, in such iodizing reaction, a binding position of an iodine atom is determined in accordance with a sort of a substituent group bound to an aromatic compound. That is, the iodine atom is meta oriented, or ortho-para oriented. Here, “meta oriented” means a property that the iodine atom is bound to an aromatic compound in a meta-position with respect to a substituent group, and “ortho-para oriented” means a property that the iodine atom is bound to an aromatic compound in either an ortho-position or a para-position, with respect to a substituent group. In a case where the iodine atom is ortho-para oriented, a product in which iodine is bound in the ortho-position, and another product in which iodine is bound in the para-position, are mixed together in a resultant product of the reaction.
In the iodizing reaction in which iodine is ortho-para oriented as described above, in some cases, the product in which iodine is bound in the ortho-position, and the product in which the iodine is bound in the para-position are obtained at a ratio of substantially 1:1.
However, in recent years, there has been demand for an improvement in selectivity (hereinafter, referred to as “position selectivity” in some cases) of a binding position of an iodine atom in such iodizing reaction. Patent Literature 1 and Non Patent Literature 4 disclose a production method whose purpose is an improvement in selectivity of the binding position of iodine. Specifically, Patent Literature 1 describes that if iodine molecules are subjected to electrolytic oxidation with the use of a carbon electrode, and then toluene is iodized, a compound in which iodine is bound in the para-position can be obtained more in amount than a compound in which iodine is bound in the ortho-position. Further, Non Patent Literature 4 describes that toluene was iodized in a solution containing methyl ester orthoformate having three ester bonds, so that the product in which iodine is bound in the ortho-position, and the product in which iodine is bound in the para-position, were obtained at a ratio of 3:7.